The present application claims priority to Japanese Application(s) No(s). P2000-344233 filed Nov. 7, 2000, which application(s) is/are incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
The present invention relates to a printer, a printer head, and a method of producing the printer head. In particular, the present invention is applicable to a printer which makes use of a process of which causes ink droplets to fly out as a result of heating by a heater. The present invention makes it possible to, by preventing a thickness-direction stepped portion from being formed at least at a partition of an ink chamber as a result of disposing a wiring pattern below the partition of the ink chamber, bring an orifice plate sufficiently into close contact with what it is to be bonded to and bond it thereto.
2. Description of the Related Art
In recent years, in the field of image processing and the like, there has been an increasing need for color hard copies. To respond to this need, there has been conventionally proposed a sublimation thermal transfer process, a fusion thermal transfer process, an inkjet process, an electrophotographic process, a thermally processed silver process, and the like.
In the inkjet process, a dot is formed by causing small drops of recording liquid (ink) to fly out from a nozzle of a recording head and causing them to adhere to what is to be subjected to a recording operation. This makes it possible to output a high-quality image using a simple structure. The inkjet process is classified into, for example, an electrostatic attraction process, a continuous vibration generation process (piezo process), and a thermal process, depending on the method used to cause the ink to fly out.
In the thermal process, air bubbles are produced by heating localized portions of the ink in order to push out the ink from a discharge opening by the air bubbles, thereby causing the ink to fly out to what is to be subjected to printing. This makes it possible to print a color image using a simple structure.
A printer which operates by this thermal process is constructed using what is called a printer head, which has mounted therein a heating element which heats ink, a drive circuit based on a logic integrated circuit which drives the heating element, and other component parts.
FIG. 8 is a sectional view partly showing a thermal head of the prior art. In forming a printer head 1, an isolation area 3 (LOGOS: local oxidation of silicon) which isolates transistors is formed on a P-type silicon substrate 2, and, for example, a gate oxide film is forced at a transistor formation area remaining between portions of the isolation area 3, thereby forming MOS (metal oxide semiconductor) switching transistors 4 and MOS transistors 5 and 6 forming a drive circuit.
Next, in forming the printer head 1, after placing, for example, an insulating film, a contact hole is formed in order to form a first-layer wiring pattern 7. By the first-layer wiring pattern 7, the MOS transistors 5 and 6, forming the drive circuit, are connected to each other, thereby forming a logic integrated circuit.
Next, in forming the printer head 1, after, for example, the insulating film has been placed, sputtering is carried out in order to deposit heating element materials, such as tantalum, tantalum aluminum, or titanium nitride, in order to form resistance films in localized portions. By the resistance films, heating elements 8 which heat ink are formed.
Next, in forming the printer head 1, a contact hole is formed to form a second-layer wiring pattern 9. By the second-layer wiring pattern 9, a connection portion between the switching transistors 4 and the heating elements 8, a connection portion between the heating elements 8 and a power supply, a ground line, and the like, are formed.
Next, in forming the printer head 1, an insulating material, such as SiO2 or SiN, is deposited in order to form a protective layer 10, after which a Ta film is formed on localized portions of the heating elements 8. By the Ta film, a cavitation resistance layer 11 is formed. Next, a dry film 13 and an orifice plate 14 are successively placed upon each other. Here, the dry film 13 is formed of, for example, carbon resin. After placing it by contact bonding, portions thereof situated in correspondence with an ink chamber and an ink path are removed, after which a hardening operation is carried out. On the other hand, the orifice plate 14 is formed of a plate-shaped material which is processed into a predetermined shape so that a nozzle 15, which is a very small ink discharge opening, is formed above the heating elements 8. The orifice plate 14 is supported on the top portion of the dry film 13 as a result of adhering it thereto. When the above-described operations are carried out, the nozzle 15, an ink chamber 16, a path for guiding ink into the ink chamber 16, etc., are formed at the printer head 1.
In the printer head 1, the ink is guided to the ink chamber 16, and, by a switching operation of the switching transistors 4, the heating elements 8 generate heat in order to heat localized portions of the ink. By the heating, core air bubbles are produced at side surfaces of the heating elements 8 of the ink chamber 16. These core air bubbles combine to form film air bubbles. When pressure is increased by the air bubbles, the ink is pushed out from the nozzle 15 and flies out to what is to be subjected to printing. As a result, in a printer using the printing head 1, intermittent heating by the heating elements 8 causes the ink to successively adhere to what is to be subjected to printing, so that a desired image is formed.
Further, in the printer head 1, the switching transistors 4, which drive the heating elements 8 are controlled by the same logic integrated circuit formed by the MOS transistors 5 and 6. Therefore, the heating elements 7 are disposed very closely together, thereby making it possible to reliably drive them by their corresponding switching transistors 5, 6.
In other words, in order to obtain a high-quality printed result, the heating elements 8 need to be disposed very close to each other. More specifically, in order to obtain, for example, a 600 DPI printed result, the heating elements 8 need to be disposed at intervals of 42,333 xcexcm. It is extremely difficult to dispose individual drive elements at the heating elements 8 disposed very close to each other. Therefore, in the printer head 1, for example, switching transistors are formed on the semiconductor substrate and are connected to the corresponding heating elements 8 by an integrated circuit technology. Then, by the drive circuits similarly formed on the semiconductor substrate, the corresponding switching transistors are driven in order to make it possible to simply and reliably drive each of the heating elements 8.
However, the printer head 1 having such a structure has a problem in that it is difficult to bring the orifice plate 14 sufficiently into close contact with the dry film 13 and to bond it thereto.
More specifically, in a commonly used semiconductor integrated circuit, the first-layer wiring pattern 7 is formed with the minimum thickness required, and the second-layer wiring pattern 9, which forms a power supply line and a ground line, is made thick in order to obtain a desired current capacity.
In contrast to this, in the printer head 1, the situation is reversed with respect to the case of the commonly used semiconductor integrated circuit, so that the first-layer wiring pattern 7 is made thick, whereas the second-layer wiring pattern 9 is made thin, in order to obtain good covering property at the silicon nitride film forming the ink protective layer 10 and the tantalum cavitation resistance layer 11, which are formed above the heating elements 8.
In the printer heat 1, by virtue of such a structure, the second-layer wiring pattern 9 is formed with a thickness of the order of 1 xcexcm when an aluminum wiring pattern is used, and a stepped portion having a size of the order of 1 xcexcm is formed at the second-layer wiring pattern 9. In this way, when the stepped portion having a size of the order of 1 xcexcm is formed at the second-layer wiring pattern 9, very fine recesses and protrusions are formed at the surface of the protective layer 10, which is formed on top of the wiring patter 9, and the surface of the dry film 13. Because of the very fine recesses and protrusions, it becomes difficult to bring the orifice plate 14 sufficiently into close contact with the dry film 13 and to bond it thereto. In this connection, when the surfaces of the protective layer 10 and the dry film 13 become very uneven, ink leakage may occur.
FIG. 9A is a plan view of the printer head 1 in FIG. 8 in which the dry film 13 has been removed, and FIG. 9B is a sectional view of the printer head 1, with the sectional view being formed by cutting a plane at a base-side partition of the ink chamber in a direction perpendicular to the illustration shown in FIG. 8. In the printer head 1, when a stepped portion of a size of the order of 1 (m is produced by the wiring pattern 9, a gap is correspondingly produced between the dry film 13 and the orifice plate 14. The gap may cause ink to leak from the partition of the ink chamber. In particular, as shown in FIG. 9A, at an endmost ink chamber 16A of a heater 8, the wiring pattern 9 is not disposed at all at the partition of the ink chamber beside it, so that the area of the gap becomes large, thereby causing the ink leakage to become noticeable at this portion. The structure shown in FIGS. 9A and 9B is a type in which ink is supplied from an edge of the semiconductor substrate. In FIGS. 9A and 9B, the lamination materials other than the second-layer wiring pattern 9 are not shown, and the external shape of the dry film 13 is shown by dotted lines in FIG 9A
In view of the above-described points, it is an object of the present invention to provide a printer in which an orifice plate can be bonded by bringing it sufficiently into close contact with what it is to be bonded to, a printer head, and a method of producing the printer head.
To overcome such problems, the present invention is applied to the printer, the printer head, or the method of producing the printer head, and, by disposing a wiring pattern below a partition of an ink chamber, a thickness-direction stepped portion is prevented from being formed at least at the partition of the ink chamber.
According to the structure of the present invention, by preventing a thickness-direction stepped portion from being formed at least at the partition of the ink chamber by disposing a wiring pattern below the partition of the ink chamber, it is possible to, by using a simple structure, prevent formation of a gap between a material forming the partition of the ink chamber and a plate-shaped material, which is an orifice plate, disposed above the material forming the partition of the ink chamber. This makes it possible to prevent ink leakage, so that the orifice plate can be bonded by bringing it sufficiently into close contact with what it is to be bonded to.